Public Release: 29-Oct-2013
Weight at time of diagnosis linked to prostate cancer mortality

Men who are overweight or obese when they are diagnosed with prostate cancer are more likely to die from the disease than men who are of healthy weight, according to a Kaiser Permanente study published today in the journal Obesity Research & Clinical Practice. In patients with more aggressive forms of prostate cancer, the researchers also found an even stronger correlation between obesity and mortality.

This study included 751 Kaiser Permanente patients with prostate cancer who underwent radical prostatectomy, an operation that includes removal of the prostate and surrounding tissue. The researchers explored the association between the patients' body mass index and prostate cancer mortality, adjusted for tumor aggressiveness and other characteristics.

The researchers found men who died from prostate cancer were 50 percent more likely to be overweight or obese at diagnosis compared to men who did not die from the disease. Men with high Gleason scores, a rating of the aggressiveness of prostate cancer cells, had the highest association between BMI and death, specifically men with Gleason scores of 8 or higher. The Gleason score ranges from 2 to 10, with the highest number representing the greatest likelihood of tumor cells spreading.

"We found among patients undergoing surgical treatment for prostate cancer, weight at time of diagnosis is more strongly correlated with prostate cancer survival than many other factors researchers have studied in the past, including some prostate cancer treatments," said lead author Reina Haque, PhD, a researcher at Kaiser Permanente Southern California's Department of Research & Evaluation in Pasadena, Calif. "Moving forward, we are hoping future studies will examine the effect of weight loss and other lifestyle modifications on prostate cancer mortality."

Additional studies are needed to determine which lifestyle modifications, such as diet or exercise, could prolong a prostate cancer patient's life. Further investigation also is needed to determine if the findings of this study, which looked at men who had prostate cancer surgery, apply to men who received other treatments such as radiation or hormone therapy.

Although the connection between men's weight at prostate cancer diagnosis and likelihood of survival has been examined, many previous studies were limited by self-reported body weight data or it was unclear when the BMI data were obtained. So the link between obesity and prostate cancer mortality remains controversial. However, the methodology of this study was different because the researchers used BMI collected from medical records, instead of self-reported data. The researchers identified men who died of prostate cancer and compared their BMI at time of diagnosis to controls to determine if body weight is related prostate cancer death. The biological relationship between obesity and prostate cancer prognosis is still not understood, and is an active area of research.

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Kaiser Permanente can conduct transformational health research like this in part because it has the largest private patient-centered electronic health record system in the world. The organization's electronic health record system, Kaiser Permanente HealthConnect®, securely connects 9.1 million patients to 17,000 physicians in 611 medical offices and 38 hospitals. It also connects Kaiser Permanente's research scientists to one of the most extensive collections of longitudinal medical data available, facilitating studies and important medical discoveries that shape the future of health care delivery for patients and the medical community.

Kaiser Permanente is committed to broadening the medical community's understanding of prostate cancer and other common cancers. Earlier this year, Kaiser Permanente researchers found that taking measurements over time of prostate specific antigen (PSA), the most commonly used screening test for prostate cancer in men, improves the accuracy of aggressive prostate cancer detection when compared to a single measurement of PSA.

The U.S. National Institutes of Health/National Cancer Institute Grant R01CA100743 (SW) supported this study.

The Department of Research & Evaluation conducts high-quality, innovative research into disease etiology, prevention, treatment and care delivery. Investigators conduct epidemiology, health sciences and behavioral research as well as clinical trials. Areas of interest include diabetes and obesity, cancer, HIV/AIDS, cardiovascular disease, aging and cognition, pregnancy outcomes, women's and children's health, quality and safety, and pharmacoepidemiology. Located in Pasadena, Calif., the department focuses on translating research to practice quickly to benefit the health and lives of Kaiser Permanente Southern California members and the general population. Visit kp.org/research.

About Kaiser Permanente

Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America's leading health care providers and not-for-profit health plans. Founded in 1945, our mission is to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve more than 9.1 million members in nine states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to kp.org/newscenter.

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